The University of California, Davis (also referred to as UC Davis, UCD, or Davis) is a public teaching and research university established in 1905 and located in Davis, California, USA. Spanning over 5,300 acres (21.45 km2), the campus is the largest within the University of California system and third largest by enrollment. UC Davis is ranked as one of the top 10 public universities in the nation, and consistently ranks amongst the best universities in the world. The university has several distinguished graduate programs ranked in the top 10 in their fields by the United States National Research Council; most notable are its programs in agricultural economics, entomology, evolutionary biology, plant biology, and ecology. Additionally, the NRC placed more than a third of UC Davis graduate programs in the top 25% of their respective fields. UC Davis faculty includes 21 members of the National Academy of Sciences, 20 members of the American Academy of Arts and Sciences, 14 members of the American Law Institute, and 9 members of the National Academy of Engineering. Among other honors, university faculty, alumni, and researchers have won the Nobel Peace Prize, Presidential Medal of Freedom, Pulitzer Prize, National Medal of Science, and Presidential Early Career Award in Science and Engineering. The faculty is "highly cited" for its research according to the Institute for Scientific Information. Strengths in liberal arts and sciences and research strengths earned it membership in the Association of American Universities.

The campus was originally established as the University Farm, the agricultural extension of UC Berkeley and the second campus of the University of California system. While UC Davis' agricultural heritage remains strong, the campus has expanded over the past century to include graduate and professional programs in medicine (which includes the UC Davis Medical Center), law, veterinary medicine, education, nursing, and business management, in addition to 90 research programs offered by UC Davis Graduate Studies. UC Davis' School of Veterinary Medicine is the largest in the United States and ranked second in the nation.

The UC Davis Aggies compete in the NCAA Division I level primarily in the Big West Conference as well as Great West Conference, Pacific-10 Conference, and Mountain Pacific Sports Federation. In its first year of full Division I status, 11 UC Davis teams qualified for NCAA post-season.